In all of my businesses, I started by putting together spreadsheets of my expenses, which allowed me to calculate how much revenue I needed to break even and keep the lights on in my office and my apartment. I wrote overviews of what I was selling, why I thought the business made sense, an overview of my competition, why my product and/or service would be important to my customers and why they should buy or use it. All of it went down on a piece of yellow paper or in a word processing file, and none of it cost me more than the diet soda I was drinking while I was writing it up.